The present invention relates to a new and improved rotor braking apparatus at each spinning unit of an open-end spinning machine, at which spinning unit, for stopping the rotor, said rotor is arranged to be pivotable from an operating position away from a drive belt into an idle position.
In an operating open-end spinning machine the individual rotors at each spinning position are driven by a common tangential drive belt. For eliminating thread breakages and for cleaning purposes there is required the possibility of uncovering and stopping the rotor without necessitating interruption of the spinning process at the other spinning units.
In a known open-end spinning machine the rotor of an individual spinning unit is uncovered by pivoting away part of the spinning unit housing from the machine frame. During said pivoting motion there is also released the fixation of a rotor support housing, receiving the rotor and its drive shaft, on the spinning unit housing in such manner that the rotor support housing, under the influence of its own weight, effects a downward pivoting motion until a brake lever pivotably arranged at the lower side of the rotor support housing contacts a rail of the machine frame and is pressed-on by the weight of the housing. By virtue of this pivoting motion the drive shaft of the rotor is pivoted away from the tangential belt driving it from above and comes to contactingly rest on the brake shoe, the friction lining or coating of which brakes the drive shaft and stops the rotor.
According to another known open-end spinning machine the rotor also is uncovered by pivoting part of the spinning unit housing, but without moving the rotor and its support housing. In this machine the tangential drive belt at each spinning unit is guided over a contact or presser roll mounted on a rod and during the spinning operation is pressed by the contact or presser roll against the drive shaft of the rotor. For stopping the rotor the rod is shifted by activating a brake lever in such manner that the contact or presser roll with the tangential drive belt is lifted off the rotor drive shaft on the drive side and that the rotor drive shaft is stopped on the opposite side by a brake also mounted on the rod.
Furthermore, from German Pat. No. 2,109,975 there is taught to the art an open-end spinning machine in which a brake is activated as a part of the spinning unit housing is opened, without pivoting the rotor, which brake mechanism lifts the tangential drive belt off the rotor shaft and presses a brake lining against the rotor shaft. Using an additional brake lever the brake mechanism in this spinning machine also can be activated without opening the part of the spinning unit housing, in such manner that repiecing of broken thread ends should be rendered possible without cleaning the rotor and without opening the part of the spinning unit housing. This machine, however, is not feasible for automatic repiecing and starting the spinning process, since automatic operation of the large and cumbersome brake lever requires complicated mechanisms.
Upon cleaning of the rotor or upon elimination of an end or thread breakage, during which process the rotor of course is also cleaned, the spinning process is to be restarted. The manual restarting process requires great skill on the part of the operator as only the short time interval, during which the drive shaft of the rotor is again contacted by the tangential drive belt and is accelerated to the operational speed, is available for piecing-up the broken end. The technological process of piecing of the end is optimally effected in the rotor within fractions of a second, as required by the process, only within a very small range of rotational speeds. During manual piecing it thus is extremely difficult to catch this optimum range. At very high rotor speeds which are increasingly required, satisfactory manual piecing even can become unpracticable, so that only an automatic restarting of the spinning process can be considered.
Instead of providing each spinning unit with a complicated and expensive restarting device, a restarting device has been proposed which is supported on a rail on the open-end spinning machine and which can be moved along the machine.
For piecing-up, the device is moved to any desired spinning unit where the restarting of the spinning process is effected automatically. Since a device of this type can operate on all spinning positions of a machine, it is economically more feasible than an automatic restarting device provided at each spinning unit.
The restarting device controls all operations of the restarting of the spinning process and in part effects them itself according to a spinning restarting program which can be optimally adjusted in accordance with the characteristics of the yarn to be spun. Included in these functions are also the releasing of the brake and the acceleration of the drive shaft of the rotor at the right moment in time in such a manner that the rotor, during the piecing process, is driven at a speed within the appropriate range of rotational speeds at the time when the fibre ring in the rotor required for piecing has just been formed and at the time when the piecing yarn end has just been brought back into the rotor. In this manner the rotor is accelerated to the higher operational speed only after completion of the piecing action at a speed within the optimum range of rotational speeds.
In machines with pivotably arranged rotors automatic piecing using a travelling piecing device presents difficulties as the rotor cannot be stopped in its spinning operating position.